Ivan strangled Till in a way that would be lethal
Whether or not he intended to kill him is another matter but pressing on Till's vocal cords like this is deadly. My friend, who's a medical resident, explained Ivan's thumbs are pushing on either side of the larynx. If the hyoid bone (at the top) is broken, it can cause severe damage to the airway. (The middle image below shows where Ivan's thumbs are pressing.)
I questioned if Ivan's thumbs weren't pressing on the sternocleidomastoid muscle instead. The middle image is what he returned to me (blue representing Till's voice box/windpipe and red the sternocleidomastoid):
"Isn't this the same method used for breath play?"
Fans have claimed Ivan is choking Till the way you would for erotic asphyxiation. The main problem with this argument is: there is no guaranteed "safe" way to choke someone.
The "method" used for breath play is pressing on the carotid arteries while avoiding pressure on the windpipe. This decreases blood flow to the brain both directly through constriction of the arteries and indirectly through compression of the baroreceptors triggering decreased blood pressure and heart rate. This can lead to cardiac arrest as well as permanent brain damage.
There are numerous ways breath play can be fatal including: cardiac arrest, respiratory alkalosis (decreased carbon dioxide increases blood pH), metabolic acidosis (decreased oxygen decreases blood pH), rupture of the windpipe, fracture of the larynx, blood vessel damage, stroke, seizures, and aspiration (saliva, vomit, etc. gets into airway/lungs). You cannot predict when someone will go unconscious and detection of an abnormal heart rhythm can already be too late.
Even if Ivan had strangled Till in the same manner as erotic asphyxiation, it would remain potentially lethal.
"Shouldn't Till have struggled?"
Another claim has been that Till would have autonomically struggled rather than going still. Research does not support this: there is no indication there is a universal reflex that occurs in all cases of strangulation. Not all strangulation victims have shown defensive movements.
Was this Ivan's intention?
My first impression from the Round 6 Behind was that Ivan had tried to kill Till, because he didn't know what he wanted to do. Vivinos explained:
With [the second draft], however, we felt that Ivan's emotions weren't being conveyed fully - so we decided to revise it once again. We made it so that viewers wouldn't be able to fully grasp Ivan's true feelings. After all, he's the only one who will ever know how he truly feels. You can't just move on from such long, deep-seated emotions in such a short time. Ivan tries to strangle Till, then kisses him, stares at him yearningly, and murmurs nonsense. His contradicting actions show his clashing emotions - he is both sure and unsure at the same time.
It's also explained that "in the end [Ivan] pours his emotions out and acts like a child." It's repeated again later that Ivan is "emotionally immature" and "expresses his emotions like a child." This gave me the impression that Ivan is just acting out and trying everything. He isn't acting with a plan in that moment, he is just expressing his emotions in every way possible.
However, in the most recent Q&A during Animate Thailand, it's answered Ivan strangled Till with the intent for Till to survive.
This brings a lot of questions I can't answer. When did Ivan decide strangling Till would be the best way to save him? Did he originally try to kill Till and then shifted his goal to saving him instead? Did he plan to strangle him from the start? Did he have a plan at all?
Since this is a rare moment Ivan's behavior is being driven by his emotions, perhaps - much like Till's character - we cannot assess his actions logically. At some point, Ivan felt that this is what he needed to do to keep Till alive. There wasn't a plan, a structure, or a methodology. Ivan either didn't know or didn't even consider he could accidentally kill Till. He didn't realize strangulation can be fatal even without constricting his air supply. He only knew if he used violence to be disqualified - to be shot down - then Till would win by default.